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Publication numberUS4410377 A
Publication typeGrant
Application numberUS 06/361,638
Publication dateOct 18, 1983
Filing dateMar 25, 1982
Priority dateMar 25, 1982
Fee statusLapsed
Publication number06361638, 361638, US 4410377 A, US 4410377A, US-A-4410377, US4410377 A, US4410377A
InventorsKarl O. Christe, William W. Wilson
Original AssigneeThe United States Of America As Represented By The Secretary Of The Army
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Tetrafluoroammonium hexafluorotitanate, alkali metal fluoride
US 4410377 A
Abstract
Improved compositions are described for solid propellant NF3 -F2as generators using (NF4)2 TiF6 and clinkering agents derived from LiF, KF, and NaF, either alone or in mixtures.
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Claims(6)
We claim:
1. Solid propellant NF3 -F2 gas generator composition comprising (NF4)2 TiF6 with LiF as a clinker forming agent.
2. Solid propellant NF3 -F2 gas generator compositions according to claim 1 wherein the mole ratio of LiF to (NF4)2 TiF6 is from 1 to 2.4.
3. Solid propellant NF3 -F2 gas generator composition comprising (NF4)2 TiF6 with NaF as a clinker forming agent.
4. Solid propellant NF3 -F2 gas generator compositions according to claim 3 wherein the mole ratio of NaF to (NF4)2 TiF6 is from 1 to 2.4.
5. Solid propellant NF3 -F2 gas generator compositions comprising (NF4)2 TiF6 with mixtures of LiF with heavier alkali metal fluorides MF, where M is selected from Na and K, as a clinker forming agent.
6. Solid propellant NF3 -F2 gas generator compositions according to claim 5 wherein the mole ratio of LiF and MF to (NF4)2 TiF6 is from 1 to 2.4.
Description
DEDICATORY CLAUSE

The invention described herein was made in the course of or under a contract or subcontract thereunder with the Government and may be manufactured, used, and licensed by or for the Government for governmental purposes without the payment to us of any royalties thereon.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to improved compositions for solid propellant NF3 -F2 gas generators, useful, for example, in chemical HF-DF lasers.

2. Description of Prior Art

NF4 + salts are the key ingredients for solid propellant NF3 -F2 gas generators, as shown by D. Pilipovich in U.S. Pat. No. 3,963,542. These propellants consist of a highly over-oxidized grain using NF4 + salts as the oxidizer. Burning these propellants with a small amount of fuel, such as aluminum powder, generates sufficient heat to thermally dissociate the bulk of the oxidizer. This is shown for NF4 BF4 in the following equation:

NF4 BF4 →NF3 +F2 +BF3 

As can be seen from the equation the gaseous combustion products contain the volatile Lewis acid BF3. This disadvantage of a volatile Lewis acid byproduct is shared by most known NF4 + compositions. These volatile Lewis acids possess a relatively high-molecular weight and a low γ value (γ=Cpi /Cvi), relative to the preferred diluent helium and frequently act as a deactivator for the chemical HF-DF laser. Consequently, these volatile Lewis acids must be removed from the generated gas prior to its use in an efficient chemical laser. Based on the state of the art, heretofore, this would be achieved by adding a clinker forming agent, such as KF, to the solid propellant formulation. The function of this additive served to convert the volatile Lewis acid, such as BF3, to a non-volatile salt as shown by the following equation:

KF+BF3 →KBF4 

Since the addition of KF significantly increases the weight of the formulation while the amount of evolved NF3 and F2 remains the same, the yield of NF3 and F2 per pound of formulation is decreased. For NF4 BF4 based formulations, the replacement of KF by the lighter alkali metal fluorides NaF or LiF would theoretically improve the obtainable NF3 -F2 yield, but was found to be impractical due to the insufficient thermal stability of NaBF4 and LiBF4, resulting in incomplete clinkering of the BF3.

The use of self-clinkering formulations based on (NF4)2 TiF6 has previously been proposed by Christe et al (U.S. Pat. No. 4,152,406) as means of increasing the theoretically obtainable NF3 -F2 yield relative to that of the state of the art NF4 BF4.1.2KF formulation. However, test firings of (NF4)2 TiF6 based formulations showed that the relatively high volatility of TiF4 (boiling point of 284 C.) resulted in the deposition of TiF4 throughtout the whole gas generator system. To eliminate TiF4 from the generated gas, KF had to be added to the (NF4)2 TiF6 based formulations. This necessary KF addition lowered the theoretically obtainable NF3 -F2 yield to a value of 39.5 weight % which is comparable to that of 38.5 weight % of the KF clinkered NF4 BF4 system and thus eliminated most of the improvement offered by the use of (NF4)2 TiF6.

BRIEF SUMMARY AND OBJECTS OF THE INVENTION

The above described problem of obtaining an (NF4)2 TiF6 based formulation of significantly higher performance than that offered by the state of the art NF4 BF4.1.2KF system is overcome by the present invention. We have found that, contrary to NF4 BF4, (NF4)2 TiF6 forms thermally stable clinkers with the lighter alkali metal fluorides NaF and LiF and that less than stoichiometric amounts of these alkali metal fluorides are required for the formation of a stable clinker due to the ability of TiF4 to form polytitanate anions. The improvements resulting from this concept are summarized in Table 1.

              TABLE I______________________________________Theoretical Yields of Usable FluorineSystem          F Yield (Weight %)______________________________________NF4 BF4.1.2KF           38.7(NF4)2 TiF6.2.4KF           39.5(NF4)2 TiF6.2.4NaF           42.9(NF4)2 TiF6.2.4LiF           47.0(NF4)2 TiF6.1.2NaF           48.4(NF4)2 TiF6.1.2LiF           50.9______________________________________

Accordingly, it is an object of the present invention to provide high performing solid propellant NF3 -F2 gas generator formulations based on (NF4)2 TiF6 and low molecular weight alkali metal fluorides.

This and other objects and features of the present invention will be apparent from the following examples. It is understood, however, that these examples are merely illustrative of the invention and should not be considered as limiting the invention in any sense.

DETAILED DESCRIPTION OF THE INVENTION EXAMPLE 1

A formulation containing 81.44 weight % (NF4)2 TiF6, 14.71 weight % LiF and 3.83 weight % Al was fired in a typical gas generater. Smooth burning was observed. Disassembly of the generator after completion of the test showed that the desired clinker had formed in the combustion chamber with essentially no TiF4 deposited in the coolant pack section of the generator. The clinker was shown by chemical analysis and vibrational spectroscopy to consist mainly of M2 TiF6 where M is Li.

EXAMPLE 2

A formulation containing 85.2 weight % (NF4)2 TiF6, 3.8 weight % LiF, 8.5 weight % KF and 2.5 weight % Al was fired in a typical gas generator. Again essentially complete clinkering of the TiF4 was observed and the clinker was shown by elemental and spectroscopic analysis to consist mainly of M2 Ti2 F10 where M is Li and/or K.

EXAMPLE 3

A formulation containing 86.0 weight % (NF4)2 TiF6, 7.3 weight % NaF, 6.7 weight % KF and 2.5 weight % Al was fired in a typical gas generator. Again essentially complete clinkering of the TiF4 was observed and the clinker was shown by elemental and spectroscopic analyses to consist mainly of M2 Ti2 F10 where M is Na and/or K.

Obviously, numerous variations and modifications may be made without departing from the present invention. Accordingly, it should be clearly understood that the forms of the present invention described above are illustrative only and are not intended to limit the scope of the present invention.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US3325318 *Feb 19, 1962Jun 13, 1967Trw IncFuel system comprising sulfur hexafluoride and lithium containing fuel
US3980509 *Aug 7, 1975Sep 14, 1976Trw Inc.Fuel, polymer, plasticizer
US4001136 *Jul 1, 1975Jan 4, 1977The United States Of America As Represented By The Secretary Of The Air ForcePerfluoroammonium salts of fluorinated lewis acids, metal nitride, alkali metal fluoride
US4003771 *Aug 7, 1975Jan 18, 1977Trw Inc.Solid grain fuels containing polyphosphonitrilics difluoride for chemical lasers
US4108965 *Oct 15, 1976Aug 22, 1978Rockwell International Corporation(NF4)2 NiF6 High energy solid propellant oxidizer and method of producing the same
US4152406 *Oct 20, 1976May 1, 1979Rockwell International CorporationSelf-clinkering NF4+ compositions for NF3 -F2 gas generators and method of producing same
US4172881 *Nov 7, 1977Oct 30, 1979Rockwell International CorporationTetrafluoroammonium hexafluorophosphate
US4284617 *Nov 30, 1979Aug 18, 1981The United States Of America As Represented By The Secretary Of The NavySolid compositions for generation fluorine and gaseous fluorine compounds
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US4711680 *May 23, 1983Dec 8, 1987Rockwell International CorporationDisplacement reaction of transition metal fluoride with lewis acid
Classifications
U.S. Classification149/109.4, 149/119
International ClassificationC06D5/06, H01S3/095
Cooperative ClassificationY10S149/119, H01S3/095, C06D5/06
European ClassificationH01S3/095, C06D5/06
Legal Events
DateCodeEventDescription
Jan 5, 1988FPExpired due to failure to pay maintenance fee
Effective date: 19871018
Oct 18, 1987LAPSLapse for failure to pay maintenance fees
May 24, 1987REMIMaintenance fee reminder mailed
May 22, 1987REMIMaintenance fee reminder mailed
May 4, 1983ASAssignment
Owner name: UNITED STATES OF AMERICA AS REPRESENTED BY THE SEC
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST. SUBJECT TO LICENSE RECITED, THIS INSTRUMENT ALSO SIGNED BY ROCKWELL INTERNATIONAL;ASSIGNORS:CHRISTE, KARL O.;WILSON, WILLIAM W.;REEL/FRAME:004126/0162;SIGNING DATES FROM 19820224 TO 19820325